Setting pins to limit or focus on particular areas in your community can help avoid areas that aren't producing good leads.
This is not recommended unless you are certain that area will not be interested in your school.
If you are certain a specific area is not an area you want to target, k's algorithim ability to generate leads.
If you are certain a specific area is not an area you want to target, you can see how to drop pins in Week 5 of the Student Magnet